De Saitssure 91 



and plants with their living analogues and to determine 

 whether they differ from these." * 



One of the most interesting features of De Saussure's 

 work is exhibited in the care with which he equipped himself 

 for the study of the rocks of the region that he undertook 

 to examine and describe. Petrography was at that time in 

 a very embryonic condition. Linnaeus and Wallerius had 

 made a beginning in the definition of rocks, but Werner's 

 labours had hardly begun. The Swiss naturalist set himself 

 with his usual ardour to the study, into which he introduced 

 his accustomed order and precision. Among other aids in 

 his researches, he devised a series of experiments in fusion, 

 in order to determine for himself the probable origin of 

 different rocks, and especially to enable him to decide 

 whether certain varieties could be produced by the melting 

 of others. It will be remembered that Desmarest had pro- 

 pounded the doctrine that the basalts of Auvergne had 

 been formed by the fusion of the underlying granite by 

 volcanic fire. De Saussure, when he began to study these 

 questions, was astonished to discover how little had been 

 done in the way of experimental research into the nature 

 of rocks. He selected various Swiss granites, and found 

 that in no instance could he reduce them by fusion into 

 basalt. In case there might be any deficiency in the granites 

 of his own country, he tried the effects of a high temperature 

 on pieces of granite which he had himself collected in 

 Auvergne, but equally without success. He then ex- 

 perimented on a granite containing abundant schorl, and 

 obtained a black vesicular glass sprinkled with the white 

 grains of infusible quartz. He next took specimens of 



1 Vol. iv. p. 505. 



